Microsoft co-founder Paul Allen has spent the last six years working on a giant aircraft capable of launching rockets to space. Today, his company Stratolaunch Systems literally rolled that plane out of its hangar in the Mojave Desert for the first time ever.

It’s called the Stratolaunch aircraft, and it’s massive. The plane has a 385-foot wingspan, which makes it the largest in the world by that metric.

It weighs about 500,000 pounds dry, but that can swell to a maximum takeoff weight of 1.3 million pounds.

Stratolaunch moves all that weight across the ground on 28 wheels, and eventually will carry its cargo through the air thanks to six 747 aircraft engines.